SPINNERET

Description

[0001] The present invention relates to a spinneret for producing several filaments, comprising a plurality of perforations, each of which ends on the bottom side of the spinneret into a respective outlet opening for pressing a thermoplastic there through for forming the filaments, wherein the outlet openings are arranged in rows which extend along a cooling direction, from one side of the spinneret to the opposite side.

[0002] Such spinnerets are used in an extrusion process for melt-spinning filaments. In such an extrusion process, typically, a thermoplastic which has been melted by means of an extruder, such as polypropylene, polyester or polyamide, is pressed through one or several such spinnerets to form filaments. Each spinneret is provided with a plurality of perforations, each having an access opening on the top side of the spinneret, via which the plastic is provided in the perforation and an outlet opening on the bottom side of the spinneret, through which the plastic pressed through the perforation leaves the spinneret as a filament. Thus, one or several filament bundles are formed for each spinneret.

[0003] The shape of a spinneret may be rectangular. The perforation pattern may then be rectangular, circular or arcuate or may assume any intermediate pattern. A spinneret may also be circular. In the latter case, the perforation pattern is thus also substantially arranged in a circle.

[0004] The present invention relates to such spinnerets which are used in an extrusion process, wherein the filaments which are formed by these spinnerets are cooled by means of what is referred to as transverse cooling. In this case, air is blown from one side of the filament bundle(s) formed by a spinneret at right angles to this (these) filament bundle(s). In this case, the air substantially follows a cooling direction which is directed from one side of the spinneret to an opposite side of the spinneret. At the location of the filaments, the air will be deflected locally.

[0005] With such existing spinnerets, the outlet openings are conventionally arranged in rows, wherein the rows are tilted with respect to said cooling direction, so that the air can impinge on each filament to the greatest degree. However, if the number of perforations per spinneret is increased in such an arrangement, the air will no longer be able to reach all the filaments formed thereby, but be deflected around the filament bundle, so that the filaments are cooled to an insufficient degree.

[0006] There already exist such optimized spinnerets in which the outlet openings are arranged in slightly curved rows which are substantially directed along the cooling direction, so that all filaments can again be impinged by cooling air in the case of a relatively large number of filaments formed thereby. However, also with this variant of a spinneret, the limit of the number of outlet openings per spinneret has been reached. If the number of outlet openings were to be increased further, the filaments would be cooled to an insufficient degree and/or they would start to stick together.

[0007] In the spinnerets of JP S56 107005 A and JP 2001 234425 A the outlet openings are arranged in rows which extend along the cooling direction, from one side of the spinneret to the opposite side. The spinneret of JP S 56 107005 A comprises the features of the preamble of claim 1.

[0008] In the spinnerets of US4248581A the outlet openings are arranged in rows perpendicular to the direction of cooling air, wherein the distance between the rows increases with the distance away from the source of cooling air. Within each row the distance between neighbouring outlet openings is constant.

[0009] It is an object of the present invention to provide an alternative spinneret, which can be provided with more perforations than the known spinnerets, without having to compromise on cooling of the filaments and without the filaments sticking to each other.

[0010] This object of the invention is achieved by providing a spinneret for producing several filaments, comprising a plurality of perforations, each of which ends on the bottom side of the spinneret into a respective outlet opening for pressing a thermoplastic there through for forming the filaments, wherein the outlet openings are arranged in rows which extend along a cooling direction, from one side of the spinneret to the opposite side, wherein these rows are arranged increasingly close together, away from a line, along this cooling direction and through the centre of the spinneret and wherein the outlet openings in each row are arranged increasingly far apart, viewed along the cooling direction.

[0011] When fitting this spinneret in an extrusion device for forming filaments, said cooling direction will coincide with the direction in which air is blown by means of a cooling device to cool the formed filaments.

[0012] Since the outlet openings are arranged in rows along this cooling direction, more outlet openings per spinneret may be provided, in which case the cooling air can still reach all filaments formed thereby, without the air flow being deflected around the filament bundle. Just as with the optimised prior-art spinnerets, these rows may be slightly curved, but preferably they are arranged in straight lines.

[0013] By arranging the rows increasingly close together away from the centre of the spinneret, the density of the outlet openings further from the centre of the spinneret is greater than closer to the centre of the spinneret, viewed at right angles to the cooling direction. Thus, the cooling air can reach as many outlet openings as possible to a maximum degree. In this way, a large filament mass can be cooled in an efficient manner. The plastic mass is distributed as well as possible across the entire surface area of the spinneret.

[0014] By means of an arrangement of the outlet openings according to the present invention, it is now possible to provide around 255 outlet openings on the same surface area of a spinneret on which commonly around 72 outlet openings were provided and on which, according to the optimized arrangement, around 181 outlet openings were provided, without compromising the cooling of the various filaments and without the filaments sticking to each other.

[0015] In order to be able to use the cooling air to the maximum degree for cooling the filaments, the distance between successive rows is preferably at most 5 times the diameter of each perforation. The diameter of such a perforation is assumed to be the diameter of the smallest circumscribed cylinder thereof.

[0016] The distance between successive rows is furthermore preferably at most 3 times the diameter of each perforation and still more preferably at most 2.5 times this diameter. In addition, this distance is preferably at least 1.25 times the diameter of each perforation and still more preferably at least 1.5 times this diameter.

[0017] In this way, cooling air can flow between these rows, with the cooling power of the air flow still being used to cool the filaments.

[0018] The outlet openings may furthermore also be arranged in curved lines in order to optimize cooling.

[0019] In a specific embodiment of a spinneret according to the present invention, the outlet openings are arranged in circular arches, with more than two outlet openings per circular arch.

[0020] More specifically, the circles of these circular arches then preferably have a common tangential tangent.

[0021] This common tangential tangent then preferably extends at right angles to the cooling direction.

[0022] Furthermore, this common tangential tangent is preferably arranged behind the spinneret, viewed along the cooling direction. Alternatively, but less preferably, this common tangential tangent may also be arranged in front of the spinneret, viewed along the cooling direction.

[0023] In an embodiment of a spinneret according to the present invention in which the outlet openings are arranged in circular arches, these circular arches preferably have an increasingly small diameter, viewed along the cooling direction.

[0024] The exit openings of a spinneret according to the present invention may have different shapes. The shape of each outlet opening will determine the shape of the filament which is formed thereby. If such an outlet opening is, more specifically, three-lobed, then a lobe of this outlet opening is preferably arranged counter to the cooling direction in order to cool such a filament to the maximum degree.

[0025] Each perforation of a spinneret opens in an access opening on the top side of the spinneret. Towards the outlet opening, each perforation adjacent to the access opening is preferably conical in order to allow plastic to flow into each perforation to the maximum degree.

[0026] In order to optimize the flow of air through a filament bundle formed using a spinneret according to the present invention, the outlet openings in successive rows are preferably arranged offset with respect to each other, still more preferably staggered with respect to each other.

[0027] A spinneret according to the present invention is preferably circular.

[0028] The outlet openings are preferably arranged substantially inside a circle.

[0029] The present invention will now be explained in more detail by means of the following detailed description of a preferred embodiment of a spinneret according to the present invention. The sole aim of this description is to give illustrative examples and to indicate further advantages and particulars of the invention and can thus not be interpreted as a limitation of the area of application of the invention or of the patent rights defined in the claims.

[0030] In this detailed description, reference numerals are used to refer to the attached drawings, in which:

• Fig. 1 shows a spinneret according to the present invention in perspective from above;
• Fig. 2 shows the spinneret from Fig. 1 in cross section;
• Fig. 3 shows the spinneret from Fig. 1 in top view;
• Fig. 4 diagrammatically shows the rows and circles in which the outlet openings are arranged in a view of the spinneret from Fig. 1.

[0031] The embodiment of a spinneret (1) according to the invention illustrated in the figures is circular and comprises 255 perforations (2). As can be seen in Fig. 2, each perforation (2) extends through the spinneret (1) from an access opening (4) on the top side of the spinneret (1) to an outlet opening (3) at the bottom side of the spinneret (1). The outlet openings (3) are arranged substantially inside a circle.

[0032] In order to form filaments, a thermoplastic, such as polypropylene, polyester or polyamide, is pressed through these perforations (2) from the top side in order to leave the spinneret (1) on the bottom side as filaments. In order to cool these filaments, air is blown onto these filaments along the cooling direction (A), which is indicated in Fig. 4. Due to the positioning of the outlet openings (3), these filaments are cooled in an optimum manner.

[0033] In Fig. 4, the outlet openings (3) are diagrammatically indicated on the spinneret (1) by means of crosses in order to illustrate their position on the spinneret (1).

[0034] These outlet openings (3) are arranged in rows (5). The horizontal lines (5) in Fig. 4 indicate these rows (5) for half the spinneret (1) on one side of line (C) along the cooling direction (A) and through the centre of the spinneret (1). Thus, it can be seen more clearly that the further these lines (5) are situated from line (C) running through the centre of the spinneret (1), the closer together these lines (5) are arranged. The illustrated spinneret (1) is symmetrical with respect to line (C) running through the centre of the spinneret (1), so that the outlet openings (3) on the other half of the spinneret (1) are arranged in corresponding rows (5) (not shown).

[0035] The diameter (d) of the perforations (2) of the illustrated spinneret (1) is 2 mm. The greatest distance between two successive rows (5) is 4.9 mm.

[0036] Vertical lines (7) through the outlet openings (3) on the line (C) through the centre of the spinneret (1) furthermore illustrate in Fig. 4 that the outlet openings (3) of the illustrated spinneret (1) on each row (5) are arranged increasingly far apart, viewed in the cooling direction (A). The greatest distance between two such successive vertical lines (7) in the illustrated embodiment is 10.4 mm.

[0037] In addition, it can be seen that the outlet openings (3) of the illustrated spinneret (1) are arranged on circular arches, the circles (6) of which are shown in Fig. 4. These circles (6) have a common tangential tangent (T) which is arranged behind the spinneret (1), viewed along the cooling direction (A), and extends at right angles to the cooling direction (A). These circles (6) have an increasingly small diameter, viewed along the cooling direction (A).

[0038] In addition, due to the position of the outlet openings (3) in said rows (5) and on said circular arches, it is ensured that the outlet openings (3) in successive rows (5) are arranged offset with respect to each other.

Claims

1. Spinneret (1) for producing several filaments, comprising a plurality of perforations (2), each of which ends on the bottom side of the spinneret (1) into a respective outlet opening (3) for pressing a thermoplastic there through for forming the filaments, wherein the outlet openings (3) are arranged in rows (5) which extend along a cooling direction (A), from one side of the spinneret (1) to the opposite side, and wherein these rows (5) are arranged increasingly close together, away from a line (C), along this cooling direction (A) and through the centre of the spinneret (1), characterized in that the outlet openings (3) in each row (5) are arranged increasingly far apart, viewed along the cooling direction (A).

2. Spinneret (1) according to Claim 1, characterized in that the distance between successive rows (5) is at most 5 times the diameter (d) of each perforation (2).

3. Spinneret (1) according to Claim 2, characterized in that the distance between successive rows (5) is at most 3 times the diameter (d) of each perforation (2).

4. Spinneret (1) according to Claim 3, characterized in that the distance between successive rows (5) is at most 2.5 times the diameter (d) of each perforation (2).

5. Spinneret (1) according to one of the preceding claims, characterized in that the distance between successive rows (5) is at least 1.25 times the diameter (d) of each perforation (2).

6. Spinneret (1) according to Claim 5, characterized in that the distance between successive rows (5) is at least 1.5 times the diameter (d) of each perforation (2).

7. Spinneret (1) according to one of the preceding claims, characterized in that the exit openings (3) are arranged in circular arches, with more than two outlet openings (3) per circular arch.

8. Spinneret (1) according to Claim 7, characterized in that the circles (6) of the circular arches have a common tangential tangent (T).

9. Spinneret (1) according to Claim 8, characterized in that the tangential tangent (T) is arranged behind the spinneret (1), viewed along the cooling direction (A).

10. Spinneret (1) according to Claim 8 or 9, characterized in that the tangential tangent (T) extends at right angles to the cooling direction (A).

11. Spinneret (1) according to one of Claims 7 to 10, characterized in that the circular arches (6) have an increasingly small diameter, viewed along the cooling direction (A).

12. Spinneret (1) according to one of the preceding claims, characterized in that each outlet opening (3) is three-lobed, wherein a lobe of this outlet opening (3) is arranged counter to the cooling direction (A).

13. Spinneret (1) according to one of the preceding claims, characterized in that outlet openings (3) in successive rows (5) are arranged offset with respect to each other.

14. Spinneret (1) according to one of the preceding claims, characterized in that this spinneret (1) is circular.

Ansprüche

1. Spinndüse (1) zum Erzeugen von mehreren Filamenten, umfassend mehrere Perforationen (2), die jeweils auf der Unterseite der Spinndüse (1) in einer jeweiligen Auslassöffnung (3) enden, zum Hindurchpressen eines Thermoplasts dort hindurch zwecks Bildens der Filamente, wobei die Auslassöffnungen (3) in Reihen (5) angeordnet sind, welche sich entlang einer Kühlrichtung (A) von einer Seite der Spinndüse (1) zu der gegenüberliegenden Seite erstrecken, und wobei diese Reihen (5) zunehmend eng beieinander, von einer Linie (C) weg, entlang dieser Kühlrichtung (A) und durch die Mitte der Spinndüse (1) angeordnet sind, dadurch gekennzeichnet, dass die Auslassöffnungen (3) in jeder Reihe (5), entlang der Kühlrichtung (A) gesehen, immer weiter auseinander angeordnet sind.

2. Spinndüse (1) nach Anspruch 1, dadurch gekennzeichnet, dass der Abstand zwischen aufeinanderfolgenden Reihen (5) höchstens das 5-Fache des Durchmessers (d) jeder Perforation (2) beträgt.

3. Spinndüse (1) nach Anspruch 2, dadurch gekennzeichnet, dass der Abstand zwischen aufeinanderfolgenden Reihen (5) höchstens das 3-Fache des Durchmessers (d) jeder Perforation (2) beträgt.

4. Spinndüse (1) nach Anspruch 3, dadurch gekennzeichnet, dass der Abstand zwischen aufeinanderfolgenden Reihen (5) höchstens das 2,5-Fache des Durchmessers (d) jeder Perforation (2) beträgt.

5. Spinndüse (1) nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass der Abstand zwischen aufeinanderfolgenden Reihen (5) mindestens das 1,25-Fache des Durchmessers (d) jeder Perforation (2) beträgt.

6. Spinndüse (1) nach Anspruch 5, dadurch gekennzeichnet, dass der Abstand zwischen aufeinanderfolgenden Reihen (5) mindestens das 1,5-Fache des Durchmessers (d) jeder Perforation (2) beträgt.

7. Spinndüse (1) nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass die Auslassöffnungen (3) in Kreisbögen mit mehr als zwei Auslassöffnungen (3) pro Kreisbogen angeordnet sind.

8. Spinndüse (1) nach Anspruch 7, dadurch gekennzeichnet, dass die Kreise (6) der Kreisbögen eine gemeinsame tangentiale Tangente (T) aufweisen.

9. Spinndüse (1) nach Anspruch 8, dadurch gekennzeichnet, dass die tangentiale Tangente (T), entlang der Kühlrichtung (A) gesehen, hinter der Spinndüse (1) angeordnet ist.

10. Spinndüse (1) nach Anspruch 8 oder 9, dadurch gekennzeichnet, dass sich die tangentiale Tangente (T) in einem rechten Winkel zur Kühlrichtung (A) erstreckt.

11. Spinndüse (1) nach einem der Ansprüche 7 bis 10, dadurch gekennzeichnet, dass die Kreisbögen (6), entlang der Kühlrichtung (A) gesehen, einen zunehmend kleinen Durchmesser aufweisen.

12. Spinndüse (1) nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass jede Auslassöffnung (3) dreilappig ist, wobei ein Lappen dieser Auslassöffnung (3) entgegen der Kühlrichtung (A) angeordnet ist.

13. Spinndüse (1) nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass Auslassöffnungen (3) in aufeinanderfolgenden Reihen (5) zueinander versetzt angeordnet sind.

14. Spinndüse (1) nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass diese Spinndüse (1) kreisförmig ist.

Revendications

1. Filière (1) destinée à produire plusieurs filaments, comprenant une pluralité de perforations (2), chaque perforation se terminant sur le côté inférieur de la filière (1) dans une ouverture de sortie respective (3) afin de presser un thermoplastique à travers celle-ci pour former les filaments, dans laquelle les ouvertures de sortie (3) sont disposées en rangées (5) qui s'étendent le long d'une direction de refroidissement (A), depuis un côté de la filière (1) jusqu'au côté opposé, et dans laquelle ces rangées (5) sont disposées de plus en plus proches les unes des autres, en s'éloignant d'une ligne (C) le long de cette direction de refroidissement (A) et à travers le centre de la filière (1), caractérisée en ce que les ouvertures de sortie (3) de chaque rangée (5) sont disposées de plus en plus espacées les unes des autres, vues le long de la direction de refroidissement (A) .

2. Filière (1) selon la revendication 1, caractérisée en ce que la distance entre des rangées successives (5) est au maximum égale à 5 fois le diamètre (d) de chaque perforation (2).

3. Filière (1) selon la revendication 2, caractérisée en ce que la distance entre des rangées successives (5) est au maximum égale à 3 fois le diamètre (d) de chaque perforation (2).

4. Filière (1) selon la revendication 3, caractérisée en ce que la distance entre des rangées successives (5) est au maximum égale à 2,5 fois le diamètre (d) de chaque perforation (2).

5. Filière (1) selon l'une quelconque des revendications précédentes, caractérisée en ce que la distance entre des rangées successives (5) est au moins égale à 1,25 fois le diamètre (d) de chaque perforation (2) .

6. Filière (1) selon la revendication 5, caractérisée en ce que la distance entre des rangées successives (5) est au moins égale à 1,5 fois le diamètre (d) de chaque perforation (2).

7. Filière (1) selon l'une quelconque des revendications précédentes, caractérisée en ce que les ouvertures de sortie (3) sont disposées en arcs circulaires, avec plus de deux ouvertures de sortie (3) par arc circulaire.

8. Filière (1) selon la revendication 7, caractérisée en ce que les cercles (6) des arcs circulaires possèdent une tangente tangentielle commune (T).

9. Filière (1) selon la revendication 8, caractérisée en ce que la tangente tangentielle (T) est disposée derrière la filière (1), vue le long de la direction de refroidissement (A).

10. Filière (1) selon la revendication 8 ou 9, caractérisée en ce que la tangente tangentielle (T) s'étend à angle droit par rapport à la direction de refroidissement (A).

11. Filière (1) selon l'une quelconque des revendications 7 à 10, caractérisée en ce que les arcs circulaires (6) présentent un diamètre de plus en plus petit, vus le long de la direction de refroidissement (A) .

12. Filière (1) selon l'une quelconque des revendications précédentes, caractérisée en ce que chaque ouverture de sortie (3) comporte trois lobes, dans laquelle un lobe de l'ouverture de sortie (3) est disposé à l'encontre de la direction de refroidissement (A).

13. Filière (1) selon l'une quelconque des revendications précédentes, caractérisée en ce que les ouvertures de sortie (3) en rangées successives (5) sont disposées décalées les unes par rapport aux autres.

14. Filière (1) selon l'une quelconque des revendications précédentes, caractérisée en ce que la filière (1) est circulaire.

Drawing